Reactance coil



E. G. SOHLBERG March 18, 1924.

REAGTANCE COIL Filed Feb. 26 1923 3 Sheets-Sheet 1 Inventor" Erik G.5ohlbeng by H is Attorny.

March 18, 1924. 1,487,614

E. G.- SOHLBERG RBAca'McncoIL Filed Feb. 26 1923 3 Shaets5heet 2 InventoY:

a q ErikGnSohlbeF byflow His Attomey.

E. G. SQHLBERG REAC'I'ANGE COIL March 18, 1924; 1,487,614

Filed Feb.926, 1923 5 Sheets-Sheet 5 Inventor":

Erik G.Sohlbe:8

H is Attorney Patented Mar. 18, 1924.

ERIK G. BOHLBEBG, 0F SOE'ENECTADY, NEW YORK,

comm, AlOOBPQRATION OI NEW YORK.

w BELC'TANCE COIL.

. i I I Application fled February 26, 1928. Serial 110. 821,148.

To all whom it may comm:

Be it known that I, ERIK G. Sonnnnns, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain newand useful Improvements in Reactance Coils, of which the following is a specification. s

My invention'relates to reactance coils and more particularly to a type of protective reactor adapted to .be so mfluenced by changes in current strength "as automatically to vary its own reactance and thus to provide protection or regulation for alter-- nating current circuits and. apparatus.

Some electrical circuits ares'ubje'cted at times to conditions or influences tending to cause abnormally high and dangerous increases in potential and current and it is the general object of this invention to my vide a variable reactance coil which automatically increase the reactance of an electrical circuit to prevent the occurrence of potentials and currents exceeding safe maximum limits. The invention has utility in connection with a. number of different types of circuits among which may be mentioned outdoor power and transm ssion circuits and the supply circuits for some ty of electrical mac mery such as induction motors.- Power and transmission circuits.

are frequently subjected to disturbances such as may be caused by lightning, switching, operations, breakdown of mu to short circuits and grounds. Such disturbances often tend to cause increases in potential and current to several or,many times their normal values resultin in injury to circuits and Wai miparatus an interruption to service. en a supply circuit for an induction motor is closed to start the motor, the tendemg; is for a starting current to build up sud nly to a value considerably above normal and afterward to decrease to normal value as the machine comes up to speed. In such instances as these, the invention ofiers a' means for guickly and automatically introduci suicient reactance into a circuit under a nor- The principles of the invention will be described in connection with the accompanying drawings in which Fig. 1 is a longitudinal sectional view of a reactance coil the sprin constructed in accordance with the invention; Fig. 2 is a diagrammatic view showmg the arrangement of the conductor in the specific form of coil shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 but with the'coiled condubtor collapsed or drawn to gether to provide maximum inductance Fig. 4 is a cross section on the line 4-4 0 ns'sronoa r0 em mare I Fig. 3; Fig. 5 shows a form of clamp which may be used in supporting the conductor of Figs. 1 and 3; 1g. 6 is a longitudinal sectional view of a modified form of the invention and Fig. 7 is a view similar to Fig. 6 but with the coiled conductor collapsed. Like reference characters indicate similar parts in the difierent figures of the draw- 1n Q In the particular form of the invention disclosedin Figs. 1 to 5 inclusive, there is shown a continuous coiled conductor 1 comprising an inside la er and an outside layer latin material. The space is c osed at its annular end pieces 5 and 6. A ringshaped laminated outer core member 7 sur-v ends rounds the coiled conductor 1 and its cas 'ing 2 and a second laminated core member 8 fits inside the conductor and its casing. The terminals 9 and 10 of thetonductor 1 are near the center of the outer layer of turns and are brought out through .insu lated openings through the wall 2 and the outer core member 7. The conductor therefore extends from one of these terminals through approximately half the outer layer of turns, thence through the inner layer of turns and thence through the other half of the outer layer to the other terminal as most clearly disclosed in Fti 2. The conductor 1 is preferably forme of some suite able resilient material and is. normally distended or expanded with itsturns spaced apart as indicated in Fig. 1. A resilient spring 11 between the inner and outer layers of the conductor 1 supports and reinforces the conductor, being secured mechanically to the conductor at suitable ptfgg: throughout its length b clamps 12. se clamps 12 are insulate from the conductor 1 and 11 to prevent short circuiting sectionso the conductor.

A flow of current in the conductor 1 induces a magnetic field which of course tends to cause the coil to colla se or contract into the position shown in ig. 3. Because of the normal spacin of, the turns of the conductor, however, t ere is large leakage of the magnetic flux and the normal reactance introduced b the coil into a circuit is therefore low. The strength of the condoctor 1 and its supporting sprin 11 opposes the force of the magnetic eld and under normal conditions maintains the conductor in distended position with its turns spaced apart. The strength of the conductor 1 and spring 11 is such, however, as to be overcome by the increased magnetic field induced by a predetermined abnormal current approaching" dangerous values, the turns of the conductor being quickly drawn to ether as indicated in Fig. 3. In the collapsed condition of the coiled conductor, the leakage of magnetic flux is negligible or slight and the coil has much greater reactance than when in its normal distended position. The current is thus limited to safe soon as the cause tending to create the abnormal current or voltage is removed, the

' coiled conductor quickly expands, thus antomatically decreasin mal value and again operation of the circuit. Lightning, short circuits and other sudden changes in circuit conditions often tend to create extremely rapid increases in voltage and current values and it is important in such cases that any protective means relied upon become efl'ectrve quickly and before the voltage and current have had time to become dangerous By locating the coil terminal near the center of thecoil as in the preferred prrangementwhich has been described, the coil may be completely collapsed without movi n any turn more than a proximately half-t e length of the coil. he time required for the reactance of the coil to change is therefore a minimum. A rapid increase in the reactance of the coil at the time when it is most needed is further contributed to by the relative motions of the several turns of the coil. As the coil rapidly collapses and the spacin of the turns decreases, each turn is cau to cut through the magnetic fields of force surrounding adjacent turns. This induces a counter electromotive force in the coil which its reactance to nor;- permitting normal to some extent aids the natural reactance.

instant during the collittle effect on the low reactance of the expanded coil but effects a large increase in reactance when the coil is collapsed.

The modified construction shown in Figs 6 and 7 is similar to the construction alrea y described and corresponding parts are indicated by the same reference characters. Laminated annular core members 20 and 21 are, however, attached to the outer ends of the reactive coiled conductor and are moved toward and from the main inner and outer core members as the coil collapses and expands. When the coil is collapsed, these core members 20 and 21 serve to close the gaps at the ends of the coil as shown in lg. 7, thus still further increasing. the reactance of the collapsed coil. The inertia of the core members 20 and 21 reduces somewhat the speed of the action of the coil but this is not objectionable unless extreme speed is necessary. l

In both forms of the invention which have been described, the coiled conductor is aided in opposing the pull of its magnetic field by a resilient spring. Under some conditions, it may be found that the resiliency of the conductor itself will offer sufiicient opposition to the pull of the magnetic field and obviously the spring may then be omitted. It may also be found desirable at times to rely wholly on the resiliency of a supporting s rin as the force opposing the magnetic fie d o the conductor, the resiliency of the conductor itself beivrz gx negli 'ble.

at c aim as new and desire to secure by Letters Patent of the United States, is,-

1. A reactor comprising a supporting structure, and a resilient conductive coil having a portion fixed to said supporting structure, other portions of said coil being movable toward said fixed rtion under the influence of the magnetic field induced by a current in the coil to increase the reactance of the coil.

2. A reactor comprising a supporti structure, and a. resilient conductive coi havin an intermediate portion thereof fixed to 'sai supporting structure, the end portions of sai coil being movable toward said intermediate fixed portion under-theinfluence of the magnetic field induced by 8. current in the coil to increase the reactance of the coil.

3. A reactor comprising a supporting structure, and a resilient conductive coil having an intermediate portion thereof fixed to said supporting structure, the terminals of the coil being near said fixed portion thereof, and the end portions of said coil being movable toward said fixed intermediate portion and terminals under the influence of the m netic field induced by a current in the coi to increase the reactance of the coil.

4. A reactor comprising a supporting lll structure, a conductive coil having a portion fixed to said supporting structure, other'portions of said coil being movable toward said fixed portion under the influence of the magnetic field induced by a current in the coil to increase the reactance of the'coil, and a resilient spring attached to said coil to oppose the force of the magnetic field.

5. A reactor comprising a conductive coil collapsible under the influence of the m netic field induced by a current in the (:36, said coil havin its terminals disposed intermediate its en 3.

6. A reactor comprising a conductive coil collapsible under the influence of the m netic field induced by a current in the coil, said coil includi a plurality of series connected layers wit coil terminals connected at an intermediate portion of one of said layers.

7. A reactor comprising a conductive coil collapsible under the influence of the magnetic field induced by a current in the coil, and means for supporting and guiding the r turns of the coil as the coil collapses.

8. A reactor comprising a conductive coil collapsible under the influence of the mag netic field induced by a current in the co and a magnetic core member adjacent said coil and shorter thanthe coil when expanded.

-9. A reactorcomprising a conductive coil collapsible under the influence of the ma netic field induced by a current in the cofi, and a magnetic core member adjacent said coil and of substantiallythe length of the coil when collapsed.

10. A reactor comprising a conductive coil collapsible under the influence of the magnetic field induced by a current .in the coil, and magnetic core parts fixed to relatively movable portions of said coil, whereby the spacin of said core parts may be reduced by the collapse of said coil.

11. A reactor comprising a conductive coil collapsible under the influence of the m netic field induced by a. current in the C25, inner and outer core members spaced from a movable end of said coil, and a core member attached to said movable end of the coil, whereby the latter core member may be drawn toward said inner and outer core members by the collapse of said coil;

' In witness whereof, I have hereunto set my hand this 23rd day of February, 1923.

ERIK G. SOHLBERG. 

